Rocket engine combustion chamber

ABSTRACT

A combustion chamber construction includes an inner wall having longitudinally extending cooling channels defined in the exterior thereof and an outer wall which is bonded to the inner wall by galvanizing, both the inner wall and outer wall are made of a single piece of an oxygen-free copper or equivalent material such as silver or molybdenum. The cooling channels are advantageously cut in accordance with the method of the invention such as by machining and formed with the least wall thickness in the area of the thrust nozzle and with the relatively greatest wall thickness in the area of the discharge of the combustion chamber. The internal wall thickness at the head portion of the combustion chamber is made of medium thickness. After the cooling channels are machined into the inner wall portion the channels are filled with a filler material which is electrically conductive and has a low melting point so that upon galvanizing it is melted out. In some instances an intermediate layer is positioned between an outer relatively thick and strong layer and inner wall of the combustion chamber, and the three layers are galvanized together.

United States Patent I 1 Inventors Karlsmke' 3,467,583 9/1969 Naimer H204/9 gg ig (mob K 3,501,916 3/1970 Butter 60/267 e I] Dederra, I'Ullll'Ill'lO Dreyer. Munich: Just sohlemann. FOREIGN PATENTSOnobnmn;MichadKaumanNeubibel-g 459,924 1/1937 Great Britain 60/260 allof, Germany July 9, 1969 July 27, 197i Messerschmitt-Bolkow Gwellschaftmit beschrankter Haftung Munich, Germany [32] Priority July 11,1968

[33] Germany [2 l 1 Appl. No. [22] Filed [45] Patented [73] Assignee[54] ROCKET ENGINE COMBUSTION CHAMBER 11 Claims, 5 Drawing Figs.

[52] US. Cl 60/267. 29/157 C, 204/9, 239/1211 [5i] Int. Cl ...F02k 1102,

C23b 7/00, B23p 15/26 [50] Field of Search 60/260, 267, 39.66; 204/9,25; 29/l57 C; 239/127.1

Primary Examiner-Douglas Hart Auomey-McGlew and Toren ABSTRACT: Acombustion chamber construction includes an inner wall havinglongitudinally extending cooling channels defined in the exteriorthereof and an outer wall which is bonded to the inner wall bygalvanizing, both the inner wall and outer wall are made of a singlepiece of an oxygen-free copper or equivalent material such as silver ormolybdenum. The cooling channels are advantageously cut in accordancewith the method of the invention such as by machining and formed withthe least wall thickness in the area of the thrust nozzle and with therelatively greatest wall thickness in the area of the discharge of thecombustion chamber. The internal wall thickness at the head portion ofthe combustion chamber is made of medium thickness. After the coolingchannels are machined into the inner wall portion the channels arefilled with a filler material which is electrically conductive and has alow melting point so that upon galvanizing it is melted out. In someinstances an intermediate layer is positioned between an outerrelatively thick and strong layer and inner wall of the combustionchamber, and the three layers are galvanized together.

PATENIFDJummn 3595.025

INVENTORS Karl St'cickel Carl-Helmut Dederra Kuno Dreyer Just S6hlemannMichael Kaufmann ATTORNEYS ROCKET ENGINE COMBUSTION CHAMBER SUMMARY OFTHE INVENTION This invention relates in general to a construction ofcombustion chambers and a method of making the same and in particular,to a new and useful combustion chamber for a liquid-fueled rocket enginewhich has an inner wall with a plurality of longitudinally extendingcooling channels defined therein and an outer wall covering which isgalvanized to the inner wall, and to a method of forming such acombustion chamber.

It is customary to cool liquid-fueled rocket engines by introducing atleast one of the propellant components into a feed ring which isconnected to a plurality of longitudinally extending cooling ducts whichextend along the combustion chamber wall. These propellent componentsare then collected in a ring adjacent the head portion and fed into thecombustion chamber for the combustion process. A rocket enginerepresents a complex machine which with regard to design requirementsfor the combustion process and structural strength requires contraryprovisions which must be coordinated in order to provide the mosteffective unit. The rocket combustion process takes place under extremetemperatures and requires a high pressure ratio for the achievement ofhigh efficiency. Since there is no suitable material, including metal,which can withstand the extremely high combustion chamber temperaturewithout protection, care must be taken to ensure that the amount of heatgenerated is rapidly dissipated. This function is achieved by employinga coolant which flows in association with the combustion chamber wallsand for this purpose the walls are provided with cooling passages whichmay be defined only up to the upper strength limits of the wall inquestion. Such an upper strength limit in respect to temperature andpressure is soon reached with the known constructions. Thus incombustion chambers made of steel with cast-in or otherwise worked-incooling ducts and an outer steeljacket welded on as a covering for thelatter, the relatively low thermal conductivity of the steel rapidlyputs a limit on the temperature increase which may be achieved and thusadversely affects the efficiency of the combustion process. Overheatingof the wall material will result in a heat accumulation so that the hotstrength of the material will diminish rapidly with the risingcombustion chamber temperatures. In order to control the very hightemperature, it is already known to make the combustion chamber with awall which is contacted by a wound tubular, copper cooling fluid coiland the individual coil windings are connected together by copperwelding or bronze soldering. There is a great danger with suchconstructions that the many junctions exposed directly to the combustionchamber temperatures will be thermally overstressed between individualcoil turns. It is also known to provide cooling ducts on the outside ofthe combustion chamber which includes a wall having a plurality ofwelded or soldered segments and to cover such ducts with a wire windingwhich are joined by soldering or welding. In such a construction thereis a great manufacturing difficulty insofar as it is practicallyimpossible to attach the outer winding or the outer jacket fitting in amanner such that a satisfactory welded or soldered joint exists betweenall the contact surfaces extending between the inner and outer wallportions. Unless this is done the welded or soldered joints will breakup under the combustion chamber loads and the existence of any singulardefective joint will soon result in a complete destruction of thecombustion chamber.

In addition to the internal pressure of the combustion chamber aneffective inner load for the combustion chamber and thrust nozzle wallwill result primarily from the pressure difference which exists betweenthe pressure of the injection of the propellant component flowing in thecooling ducts and the inner pressure of the combustion and thrustnozzle. The pressure is reduced from the front to the rear of thecombustion chamber and at the location to the rear of the thrust nozzleat the thrust discharge end it is only slightly above ambient pressure.This pressure difference bears on the inner wall of the combustionchamber and the thrust nozzle formed by the body of the combustionchamber in the regions of the webs between the cooling channels so thatthe individual wall elements are unduly stressed in radial directions.In addition, the joints are stressed by the differential pressures whichexist to produce tension stresses between the radially outwardlypointing surfaces of the individual webs between the cooling channelsand the exterior wall.

In accordance with the invention the disadvantages of the prior art areovercome by providing a combustion chamber construction which is capableof safely withstanding an extremely high combustion chamber presence orinjection pressure as well as extremely high combustion chambertemperatures. This is done by providing a combustion chamber having aninner wall made of a single piece of an oxygen-free copper material, or,of a material approximately equivalent in its properties, such as silveror molybdenum. The exterior of this wall is covered with a cover of amaterial. of similar properties after the cooling channels have beenworked into the exterior surface of the inner wall, such as bymachining.

In accordance with a further feature of the invention, the wallthickness of the interior wall is varied in accordance with thetemperature and pressure conditions which exist during the operation ofthe combustion chamber. For this purpose the wall is advantageously madethe thinnest in the area of thrust nozzle neck and the thickest adjacentthe thrust nozzle discharge opening. It is made of medium thicknessadjacent the combustion chamber head portion. In this manner thethickness of the interior wall is proportional to the diameter of theunit and changes over its length. Galvanize as used herein is intendedto mean electroform and electrodeposit.

Accordingly, it is an object of the invention to provide an improvedmethod of forming a combustion chamber which includes forming aninterior wall of a single piece of substantially pure oxygen-free coppermaterial or an equivalent material, machining a plurality oflongitudinally extending channels in the exterior wall, and covering theexterior of the interior wall by a cover of a similar material bygalvanizing the cover to the interior wall.

A further object of the invention is to provide a combustion chamberwhich includes an interior wall having a plurality of longitudinallyextending cooling conduits defined therein and an exterior wall which isformed and bonded to the interior wall by a galvanizing process andwhere the interior wall is made of variable thickness preferably of aminimum thickness in the nozzle neck portion.

A further object of the invention is. to provide a combustion chamberwhich is simple in design, rugged in construction, and economical tomanufacture.

The various features of novelty which characterize the invention arepointed out with particularity in the claims annexed to and forming apart of this specification. For a better understanding of the invention,its operating advantage and specific objects attained by its use,reference should be had to the accompanying drawings and descriptivematter in which there are illustrated and described preferredembodiments of the invention.

BRIEF DESCRIPTION OF THE DRAWINGS In the drawings:

FIG. I is a partial longitudinal sectional view of a combustion chamberconstructed in accordance with the inventlon;

FIG. 2 is a section taken along the line II-II of FIG. 1;

FIG. 3 is a section taken along the line III-III of FIG. 1;

FIG. d is a section taken along the line IV-IV of FIG. l; and

FIG. 5 is a view similar to FIG. 2 of another embodiment of theinvention.

DESCRIPTION OF THE PREFERRED EMBODIMENTS Referring to the drawings inparticular, the invention embodied therein in FIGS. 1 to 4 comprises acombustion chamber generally designated having a head portion generallydesignated 50A, a nozzle neck portion generally designated 50B, and arear portion or nozzle discharge portion generally designated 50C. Thecombustion chamber unit is made of a basic body or inner wall portiongenerally designated 1 which is made of an oxygen-free copper or anequivalent material such as a silver or molybdenum. It may be preparedin a traditional manner from a copper block by forging and structurallystrengthening, and preferably further machining by chip removal. Coolingchannels 2 running in longitudinal direction are machined out of thebasic body I so that webs remain between the cooling channels 2.

In accordance with the invention the channels 2 are filled with anelectrically conductive low melting point substance and an outer jacketor covering 4 preferably made of an oxygen-free copper or similarmaterial is applied over the inner wall I and galvanized to it,whereupon the filler material is melted out. This joins the jacket tothe inner wall portion 1 safely and rigidly at all points of contact ofthe webs 3.

During the forming of the cooling channels 2 consideration is given tothe operating conditions of pressure temperature which exists along thevarious portions of the combustion chamber. For this reason the variousthickness of the wall portions la, lb and which are indicated in FIGS.3, 2 and 4, respectively, are varied in accordance with the operatingconditions such that the nozzle wall thickness la is made the thinnestas indicated by the dimension X in FIG. 3. The discharge wall section50C and designated 1c is made the thickest as indicated by the dimensionZ and the wall thickness of the head portion 50A is made of anintermediate thickness Y as indicated in lb in FIG. 2. In addition, thecooling channels 2 are of the smallest cross section at the nozzle asindicated in FIG. 3 and at the Y of the widest of the cross section atthe discharge end as indicated in FIG. 4, with the cooling channelsbeing of intermediate cross-sectional area as indicated in FIG. 2 forthe head portion of the combustion chamber. The width of the coolingchannels is relatively the greatest due to the greatest diameter of theunit at the location of the discharge section 50C.

In the embodiment indicated in FIG. 5, an intermediate thin-walled layer5 is galvanized to an outer thick layer 6 and inner wall portiongenerally designated 1. The thick-walled cover 6 is made of a nickel orsimilar material having high strength characteristics in order to absorbthe high internal pressure of the combustion chamber. The thin wallintermediate layer is made of an oxygen-free material such as copperwhich is galvanized to the interior wall ll in the outer jacket 6.

With the invention there is the guarantee that a safe connection isassured everywhere between the radially outward oriented surfaces of thevarious webs 3 and the inside of the external combustion chamber andthrust nozzle wall I. Moreover, the galvanizing process represents initself a proven, technologically simple and inexpensive method forproducing the external wall. The connection reaches an optimum when theexternal wall is produced, according to the invention, from the samematerial as the basic body. Another possibility exists in the use of amaterial of high mechanical strength, such as nickel whichsimultaneously enters into a sufficiently reliable bond with copper, forgalvanizing the external wall.

Especially favorable conditions with regard to maximum heat dissipation,reliable connection of the basic body to to the external wall, andstrength are achieved with the following inventive construction of thecombustion chamberthrust nozzle unit.

A basic body which consists of oxygen-free copper or an equivalentmaterial such as silver or molybdenum and on which is galvanized athin-walled, intermediary layer, likewise of oxygen-free copper or anequivalent material such as silver or molybdenum, and a thick-walledpressure jacket of nickel or a similar material with good strengthcharacteristics, galvanized onto said intermediary layer.

The material identity between the basic body and the intermediary layerassures an absolutely reliable connection between these two componentsat their mutual relatively narrow areas of contact. In addition, thepressure jacket which encloses the intermediary layer in a formfittingmanner assures the intermediary layer of a gapless support and, withthis, its safe connection to the webs of the basic body.

The oxygen-free copper material guarantees a maximum heat flow betweenthe basic combustion chamber body directly exposed to the fire and thecoolant, due to the good heat conductivity of this metal. In addition,oxygen-free copper is virtually insensitive to harmful oxidationphenomena caused by chemically aggressive fuel ingredients duringoperation and by various manufacturing processes, such as welding andsoldering. By galvanizing a reliable connection, not directly exposed tothe fire gases, but rather directly cooled by the coolant, is assured atall areas of contact between the cover jacket and the webs of the basicbody. In addition, the invention, by the individual wall thicknessdimensioning of the cooling channels for the internal combustion chamberand thrust nozzle wall, an optimal construction is achieved in regard tocombustion chamber and thrust nozzle stresses, since these wallthicknesses are adapted to the local differential pressures occurring invarious magnitudes over the length of the combustion chamber and thrustnozzle. The cause for these differential pressures, differing by zones,is, as already mentioned, that the pressure of the combustion orpropelling gases decreases constantly from the combustion chamber up tothe thrust nozzle end, until the environmental pressure is reached,whereas the pump pressure of the coolant from the thrust nozzle end tothe combustion chamber head decreases relatively little. For thisreason, a maximum pressure is exerted against the internal thrust nozzlewall and against the bottom of the various cooling channels in the reararea of the thrust nozzle. This maximum pressure imposes a bendingstress on the bottom of the channels. At the greatest diameter of theunit, the width of the cooling channels also reaches a maximum so thatthe bending load also becomes maximal. This tendency is countered by theinvention in advantageous manner, in that here the wall thickness of thecooling channel bottoms is dimensioned the thickest at the greatestdiameter portion.

In the area of the nozzle neck, where a medium pressure is applied onthe channel bottoms, the latter are made the thinnest in advantageousutilization of the minimum cooling channel width. The inventive minimumwall thickness of the internal thrust nozzle wall and of the coolingchannel bottoms in the area of the nozzle neck meets the givenconditions advantageously. The thinnest wall thickness is at the hottestzone of the combustion chamber, Le. at the thrust nozzle portion. Theheat dissipation here is increased to its maximum value.

The medium wall thickness of the cooling channel bottoms in the actualcombustion chamber zone adjacent the head meets the stresses occurringhere best. Here at relatively small differential pressure and highcombustion chamber temperature, the width of the cooling channelsassumes a medium value.

What I claim is:

I. A combustion chamber construction for a liquid-fueled rocket enginehaving a thrust nozzle with a discharge opening comprising an inner wallbody having a plurality of longitu' dinally extending cooling channelsdefined in the exterior thereof which are adapted to be filled with atleast one fuel component, said inner wall being made of a single pieceof a metal material, and an exterior wall extending around the exteriorof said inner wall and being galvanized to said inner wall.

2. A combustion chamber, according to claim I, wherein said exteriorwall comprises oxygen-free copper.

3. A combustion chamber, according to claim 1, wherein said inner walland said exterior wall consists of one of the following materials:oxygen-free copper, silver, and molybdenum.

4. A combustion chamber, according to claim 1, wherein said exteriorwall comprises a nickel material.

5. A combustion chamber, according to claim 1, wherein said coolingchannels are of a minimum cross section adjacent said nozzle neckportion and the maximum cross section adjacent said nozzle dischargeportion and of intermediate crosssectional area adjacent said nozzlehead portion.

6. A method, according to claim 5, wherein the cooling conduits arefilled with a filler material which is electrically conductive and has alow melting point before the galvanizing of the cover to the interiorwall.

7. A combustion chamber, according to claim 1, including an intermediatelayer galvanized to the interior wall and to the exterior wall andconsists of at least one of the following: oxygen-free copper, silverand molybdenum, said exterior wall being a thick-walled pressure jacketof a metal material having high strength characteristic.

8. A combustion chamber, according to claim 1, wherein said thrustnozzle has a neck portion and wherein said cooling channels are fon'nedsuch that said interior wall has the minimum thickness adjacent thenozzle neck portion and the maximum thickness adjacent the nozzledischarge portion.

9. A method of forming a combustion chamber comprising forming theinterior wall of a single piece of at least one of the followingmaterials: copper, molybdenum, and silver, machining a plurality oflongitudinally extending cooling channels into the exterior surface ofsaid interior wall, surrounding the interior wall with a cover of amaterial similar to the interior wall and bonding the cover to theinterior wall by galvanizing.

10. The combustion chamber according to claim 1, wherein said metalmaterial comprises oxygen-free copper.

11. A combustion chamber according to claim 1, wherein said exteriorwall is a thick-walled pressure jacket of a nickel metal material havinga high strength characteristic.

1. A combustion chamber construction for a liquid-fueled rocket enginehaving a thrust nozzle with a discharge opening comprising an inner wallbody having a plurality of longitudinally extending cooling channelsdefined in the exterior thereof which are adapted to be filled with atleast one fuel component, said inner wall being made of a single pieceof a metal material, and an exterior wall extending around the exteriorof said inner wall and being galvanized to said inner wall.
 2. Acombustion chamber, according to claim 1, wherein said exterior wallcomprises oxygen-free copper.
 3. A combustion chamber, according toclaim 1, wherein said inner wall and said exterior wall consists of oneof the following materials: oxygen-free copper, silver, and molybdenum.4. A combustion chamber, according to claim 1, wherein said exteriorwall comprises a nickel material.
 5. A combustion chamber, according toclaim 1, wherein said cooling channels are of a minimum cross sectionadjacent said nozzle neck portion and the maximum cross section adjacentsaid nozzle discharge portion and of intermediate cross-sectional areaadjacent said nozzle head portion.
 6. A method, according to claim 5,wherein the cooling conduits are filled with a filler material which iselectrically conductive and has a low melting point before thegalvanizing of the cover to the interior wall.
 7. A combustion chamber,according to claim 1, including an intermediate layer galvanized to theinterior wall and to the exterior wall and consists of at least one ofthe following: oxygen-free copper, silver and molybdenum, said exteriorwall being a thick-walled pressure jacket of a metal material havinghigh strength characteristic.
 8. A combustion chamber, according toclaim 1, wherein said thrust nozzle has a neck portion and wherein saidcooling channels are formed such that said interior wall has the minimumthickness adjacent the nozzle neck portion and the maximum thicknessadjacent the nozzle discharge portion.
 9. A method of forming acombustion chamber comprising forming the interior wall of a singlepiece of at least one of the following materials: copper, molybdenum,and silver, machining a plurality of longitudinally extending coolingchannels into the exterior surface of sAid interior wall, surroundingthe interior wall with a cover of a material similar to the interiorwall and bonding the cover to the interior wall by galvanizing.
 10. Thecombustion chamber according to claim 1, wherein said metal materialcomprises oxygen-free copper.
 11. A combustion chamber according toclaim 1, wherein said exterior wall is a thick-walled pressure jacket ofa nickel metal material having a high strength characteristic.